01
No information about the cipher is provided
LHFKM GMRHC FLMMJ ULXFY JOUFC
FQFXF ZJOKP JOMMU LMRJT FFTBA
JYFFR JZFXG AWJCB ULXFI FFKRF
KPGKH RFWCF MTFRR LHFRI FMQFF
KFLWU JMUFC IOMMU FYCFF KWCYB
MFPQF CFHJG KHMJK FFPMJ PFWCY
BMMUF TMJQJ CVJOM GZMUF CFRRJ
TFMUG KHGAA FHLAH JGKHJ KLKPH
FMMUF TLCCF RMFPK JCTLA YMUFW
CYBMJ HCLBU YMFLT QJOAP PJMUG
RIOMM UFYXF LAAPF WGPFP LMMUF
RLTFM GTFMJ HJJKL KOLAA FLXFI
FRMJZ AOWVL HFKMI MUFRF WCFMW
JPFGR PJWOT FKMR
We have to solve the cipher. Considering the level and monoalphabetic substitution i.e each alphabet is replaced with other alphabet.
Quickly verifying my hypothesis by checking on quipquip I found the plaintext
AGENT ITS GREAT TO HAVE YOU HER E WEVE FOUND OUT THAT SOME EMPL OYEES OF EVIL CORP HAVE BEEN SE NDING SECRET
MESSAGES BETWEE N EACH OTHER BUT THEYRE ENCRYP TED WERE GOING TO NEED TO DECRY PT THEM TO WORK OUT IF THERES
SO METHING ILLEGAL GOING ON AND G ET THEM ARRESTED NORMALY THE C RYPTOGRAPHY TEAM WOULD DO THI S BUT THEYVE
ALL DECIDED AT THE SAME TIME TO GO ON ANUAL LEAVE B EST OF LUCK AGENT B THE SECRET C ODE IS DOCUMENTS
Correcting spaces a bit, we get the text decrypted.txt
AGENT ITS GREAT TO HAVE YOU HERE WEVE FOUND OUT THAT SOME EMPLOYEES OF EVIL CORP HAVE BEEN SENDING
SECRET MESSAGES BETWEEN EACH OTHER BUT THEYRE ENCRYPTED WERE GOING TO NEED TO DECRYPT THEM TO WORK
OUT IF THERES SOMETHING ILLEGAL GOING ON AND GET THEM ARRESTED NORMALY THE CRYPTOGRAPHY TEAM WOULD
DO THIS BUT THEYVE ALL DECIDED AT THE SAME TIME TO GO ON ANUAL LEAVE BEST OF LUCK AGENT B THE SECRET
CODE IS DOCUMENTS
Hence the code we are looking for is DOCUMENTS
Alternatively, you may look up the video writeup by @hyperreality on puzzles 01-06, they were quite informative, given that I got stuck at 04
YouTube link
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